E.B.
I'm sorry you're having to deal with such problems. My daughter has had significant problems with her skin, and the itching has been unbearable at times.
It's interesting that your problems started when you stopped taking a long-term prescription. If you feel like it, tell us what that was and why you were taking it. You might consult the pharmacist, and ask if stopping that medication cold turkey like you did could have caused the effects you're experiencing now.
Have you seen a dermatologist, and an infectious disease doctor, and a rheumatologist (that's the doctor who diagnoses Lupus and other autoimmune diseases). If not, you should. And have any of your doctors biopsied your scalp? My daughter had a skin biopsy on two occasions. They take a very small portion of skin (after numbing the area) and evaluate it at a pathology lab. The area is stitched up with just a couple of stitches.
Re-think your shampoo and conditioner. Some of the ones that are advertised as being helpful for problems are actually very harsh. Ask a pharmacist for the most mild shampoo for scalp issues. Ask the dermatologist for recommendations about how to wash your hair (how often, with what, etc).
Ask the doctors: what would you do if you were me? Can you recommend a specialist? Ask if foods or medications can cause symptoms like yours. Don't stop seeking answers.